A tray feeder includes tray supply mechanisms and arranged in parallel. Each of the tray supply mechanisms has a function of retrieving a tray from a tray housing portion by a tray retrieving unit, and transferring the pallet up to a component pickup position set in the vicinity of a height at the upper end of the tray housing portion. A lock state of a door by a door lock mechanism is released only in a state where the tray retrieving unit is located at the component pickup position and blocks an interior of the tray feeder from a head transfer space in which the mounting head transfers.